Contextual-specificity of short-delay extinction in humans: renewal of fear-potentiated startle in a virtual environment

Abstract

A recent fear-potentiated startle study in rodents suggested that extinction was not context dependent when extinction was conducted after a short delay following acquisition, suggesting that extinction can lead to erasure of fear learning in some circumstances. The main objective of this study was to attempt to replicate these findings in humans by examining the context specificity of short-delay extinction in an ABA renewal procedure using virtual reality environments. A second objective was to examine whether renewal, if any, would be influenced by context conditioning. Subjects underwent differential aversive conditioning in virtual context A, which was immediately followed by extinction in virtual context B. Extinction was followed by tests of renewal in context A and B, with the order counterbalanced across subjects. Results showed that extinction was context dependent. Evidence for renewal was established using fear-potentiated startle as well as skin conductance and fear ratings. In addition, although contextual anxiety was greater in the acquisition context than in the extinction context during renewal, as assessed with startle, context conditioning did not influence the renewal effect. These data do not support the view that extinction conducted shortly after acquisition is context independent. Hence, they do not provide evidence that extinction can lead to erasure of a fear memory established via Pavlovian conditioning.

Figure 1.

(A) Experimental protocol. Black, gray, and white bars represent CS+, CS−, and ITI, respectively. (B) Pictures of the three virtual environments: the airport, the city street, and the subway.

Figure 2.

Magnitude of the startle reflex elicited during CS+ and CS− during acquisition (context A), extinction (context B), and renewal test in the acquisition and extinction contexts. Note that there were only five blocks (instead of six blocks) of three trials per block because only 15 of the 18 trials per CS contained a startle probe. *P < 0.05.

Figure 3.

Skin conductance response (SCR) to the onset of the CS+ and CS− during acquisition (context A), extinction (context B), and renewal test in the acquisition and extinction contexts. *P < 0.05.